Case-control study of leptospirosis in Aotearoa New Zealand reveals behavioural, occupational, and environmental risk factors

Leptospirosis in NZ has historically been associated with male workers in livestock industries; however, the disease epidemiology is changing. This study identified risk factors amid these shifts. Participants (95 cases:300 controls) were recruited nationwide between 22 July 2019 and 31 January 2022, and controls were frequency-matched by sex (90% male) and rurality (65% rural). Multivariable logistic regression models, adjusted for sex, rurality, age, and season - with one model additionally including occupational sector - identified risk factors including contact with dairy cattle (aOR 2.5; CI: 1.0-6.0), activities with beef cattle (aOR 3.0; 95% CI: 1.1-8.2), cleaning urine/faeces from yard surfaces (aOR 3.9; 95% CI: 1.5-10.3), uncovered cuts/scratches (aOR 4.6; 95% CI: 1.9-11.7), evidence of rodents (aOR 2.2; 95% CI: 1.0-5.0), and work water supply from multiple sources - especially creeks/streams (aOR 7.8; 95% CI: 1.5-45.1) or roof-collected rainwater (aOR 6.6; 95% CI: 1.4-33.7). When adjusted for occupational sector, risk factors remained significant except for contact with dairy cattle, and slaughter without gloves emerged as a risk (aOR 3.3; 95% CI: 0.9-12.9). This study highlights novel behavioural factors, such as uncovered cuts and inconsistent glove use, alongside environmental risks from rodents and natural water sources.

Keywords

Leptospirosis, Zoonotic, Rodent, Livestock, Water

Citation

Nisa S, Ortolani E, Vallée E, Marshall J, Collins-Emerson J, Yeung P, Prinsen G, Wright J, Quin T, Fayaz A, Littlejohn S, Baker MG, Douwes J, Benschop J. (2025). Case-control study of leptospirosis in Aotearoa New Zealand reveals behavioural, occupational, and environmental risk factors. Epidemiology and Infection. 153.

URI

https://mro.massey.ac.nz/handle/10179/73012

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